Structural and functional aspects of biological freezing techniques.

Area of Science:

• Cryobiology
• Cell Biology
• Ultrastructural Analysis

Background:

• Cooling procedures for ultrastructural examination differ from those for cell recovery after thawing.
• High concentrations of cryoprotective agents (e.g., glycerol, dimethyl sulfoxide) can cause cell damage.
• These additives are ineffective cryoprotectants under rapid cooling conditions used for structural studies.

Purpose of the Study:

• To review the implications of differing cooling procedures for cell structure and function.
• To highlight how cryoprotective agents impact cells during low-temperature preparation and thawing.
• To explore the structural and functional interests of cells prepared using various cryobiological principles.

Main Methods:

• Review of cryobiological principles.
• Illustration using freeze-fracture and freeze substitution techniques.
• Assessment via functional assays on Chlorella sp. and mammalian tissue culture cells.

Main Results:

• Rapid cooling for structural studies does not utilize cryoprotective agents effectively, potentially causing damage.
• Cells cooled rapidly may retain unaltered structure if injury occurs during rewarming.
• Cells capable of functional recovery after thawing are often shrunken at low temperatures but structurally interesting.

Conclusions:

• Differences in cooling protocols for ultrastructural preservation versus functional recovery can lead to cell damage.
• Understanding cryoprotective agent behavior under varying cooling rates is crucial for both structural and functional studies.
• Cryobiological principles, illustrated by freeze-fracture, freeze substitution, and functional assays, are key to interpreting cell behavior during cryopreservation.